1. Field of the Invention
The present invention relates generally to optical systems. The present invention relates more particularly to micro-electromechanical systems (MEMS) for modulating optical signals.
2. Description of the Background Art
A two-dimensional projection image may be formed by using one or more linear arrays of light-modulating elements. The light-modulating elements may comprise, for example, GRATING LIGHT VALVE (GLV) devices or other types of devices that modulate optical signals in a controllable manner. Publications describing GLV devices and their application to display systems include: xe2x80x9cThe Grating Light Valve: Revolutionizing Display Technology,xe2x80x9d by D. M. Bloom, Projection Displays III Symposium, SPIE Proceedings, Volume 3013, San Jose, Calif., February 1997; xe2x80x9cGrating Light Valve Technology: Update and Novel Applications,xe2x80x9d by D. T. Amm and R. W. Corrigan of Silicon Light Machines in Sunnyvale, Calif., a paper presented at the Society for Information Display Symposium, May 19, 1998, Anaheim, Calif.; and xe2x80x9cOptical Performance of the Grating Light Valve Technology,xe2x80x9d David T. Amm and Robert W. Corrigan of Silicon Light Machines, a paper presented at Photonics West-Electronics Imaging, 1999. Each of the above-mentioned publications is hereby incorporated by reference in its entirety.
Such projection systems may be configured so that a linear array of light modulating elements modulates an incident light beam to display pixels along a column (or, alternatively, a row) of the two-dimensional (2D) image being formed. A scanning system is used to move the column horizontally such that each light-modulating element is able to generate a row of the 2D image. In this way, the entire 2D image is displayed.
One embodiment of the invention relates to a method for driving a plurality of light-modulating elements. The method includes, for each element, providing an amplitude modulation signal and providing a width modulation signal. Modulation of light by the element is determined with respect to height by the amplitude modulation signal and with respect to width by the width modulation signal.
Another embodiment of the invention pertains to an apparatus for driving a plurality of light-modulating elements. Circuitry is included that provides for each element an amplitude modulation signal at a base frequency. Circuitry is also included that provides for each element a width modulation signal at the base frequency.
Another embodiment of the invention relates to a system for modulating a plurality of micro-electromechanical (MEM) devices. The system includes a means for providing an amplitude modulation signal to each MEM device at a base frequency and a means for providing a width modulation signal at the base frequency. In addition, the system includes a clock means for providing a higher-frequency clock signal with a frequency that is a multiple of the base frequency. In this embodiment, the width modulation signal for each MEM device indicates at least one position on the higher-frequency clock signal.